After weighing his NFL option, the quarterback will play his senior season, making him a Heisman Trophy front-runner and the Trojans contenders for a national title.

Three years as USC's starting quarterback, including a record-setting junior season, made him a projected top-10 pick in the April draft.

Barkley, however, has been the poised face and voice of the program since June 2010, when the Trojans were hammered with NCAA sanctions that included a two-year bowl ban.

The pull of staying the course, of leading USC through a bowl-eligible season with what will be a projected national title contender, moved Barkley to put his dream on hold.

On Thursday in Heritage Hall, standing only a few feet from where he calmly addressed reporters after NCAA penalties came down, Barkley enthusiastically announced he was returning to USC.

"I am staying," he said, "because I want to finish what I started."

Barkley's decision is expected to make the Trojans a top-five team next season, when the former Santa Ana Mater Dei High star will be among the front-runners for the Heisman Trophy. Barkley finished sixth in Heisman balloting this season.

"It's a special, special day," said USC Coach Lane Kiffin, who learned of the decision Wednesday evening during a visit to the Barkley home in Newport Beach.

"This is a great day for USC," Athletic Director Pat Haden said, "for our family, our fans and I would say for college football as well."

Barkley's news conference was the third in recent years in which a Trojans quarterback held court in Heritage Hall to announce a decision about returning or turning pro.

In 2005, Matt Leinart said he would return to USC, drawing cheers in a packed lounge. In 2009, Mark Sanchez announced he would enter the NFL draft, creating an awkward scene with former coach Pete Carroll, who said that he disagreed with the decision.

Thursday's announcement ended on a happier note, and Carroll, now coach of the Seattle Seahawks, cheered Barkley's decision from afar.

"I thought it was awesome," Carroll, who started Barkley as a freshman, said in a telephone interview. "I would have been surprised if it went the other way. He sees the experience differently than other guys have. There's more that he'd like to do and he likes playing college football.

"He knows he's going to play in the NFL."

Barkley, 21, was the last of four prominent USC juniors to announce a decision about his future.

All-American left tackle Matt Kalil and defensive end Nick Perry are turning pro. All-American safety T.J. McDonald announced Wednesday that he would return for his senior season.

Barkley made his decision after consulting with coaches, former players, NFL personnel and agents and family and close friends.

His father, Les, said his son understood the economic ramifications of forgoing an NFL opportunity that would have netted millions of dollars.

"It was a fairly intense process because he was getting a lot of data," Les Barkley said. "We really cut it off at a certain point in time because you can't really get any more facts.

"I think we all came to the point of, 'OK, now you've got to take a step back and be contemplative and prayerful and make your decision because you're not going to get any more input.'"

Barkley's mother, Beverly, said she was prepared for her son to "take that next step" and head to the NFL.

"I didn't really know what he was going to do at all until he basically said, 'I'm 70-30' [toward staying in school], and then we really hammered him" with questions to make sure, she said.

Barkley declined to reveal details of his conversations with former USC players and others now in the NFL. But he acknowledged there was "a consensus from a lot of people about following your heart."

A few days ago, Barkley said he had "a gut feeling" about staying.

After discussing his feelings with his family, he took some time alone to finalize his decision.

"To just know for certain that that's what I wanted to do," he said. "I felt that pull in my heart."